As control identification information of a conventional optical disk, a method of recording a control track onto a part of the optical disk has been known as disclosed in, e.g., ISO (International Standard Organization) Draft Proposal ISO/DP 9171-2 (5th DP), 1.7.2 Phase encoded part (PEP).
FIG. 5 shows a format of the control track in the conventional example. As shown in FIG. 5(a) data is repetitively recorded three times on one track. As shown in FIG. 5(b), each data comprises: data of 144 bits; a sector address of 8 bits; an error detection code (CRC) of 8 bits; a preamble (PR) of 16 bits to regenerate a clock; and a synchronization bit (SYNC) of 1 bit indicative of the head of the data. Each data bit is PE (Phase Encoding) modulated as shown in FIG. 5(c), by a suitable low frequency and recorded onto hundreds of tracks so as to be read at various rotational speeds.
When the optical disk is inserted into a drive, a head is moved by a linear motor and the control track is accessed, so that the control data is read out and various kinds of information which are peculiar to the disk such as recording system, recording and reproducing conditions, recording area, and the like are known. On the basis of this disk information, the operating mode of the drive is set. Due to this, various kinds of optical disks can be used by a single drive.
According to the foregoing structure, since no track address information is recorded on the control track, the control track cannot be directly sought. Therefore, the head is once moved to a position near the control track and either some of the hundreds of control tracks are roughly read without performing the tracking control. This causes the recording capacity of the disk to be reduced and a precise mechanism to accurately seek the control track is needed for the drive. In addition, since the optical head is moved to the control track portion without using any track address, the moving speed cannot be raised. Further, a waiting time of the rotation of the disk in a rough reading operation to seek the control track is caused. Therefore, when the disk is exchanged by the drive, it takes a time to read the control data from the control track and there is a problem in that the rise-up speed of the drive becomes slow.